Backport

1. linkage->cdsz for chosen_disjuncts.
2. New two debug print functions, unused for now but used in the Wordgraph version.
3. Convenience displaying of EMPTY_WORD.zzz in debug messages, as "ø".
4. Supress printing of the empty word in the output of the "!!" command (e.g. as happens with **!!let's**).